SAN CARLOS IRRIGATION PROJECT, ARIZONA. present, probably covering the toe of the sloping rock which projects from the foot of the bluff into the gorge, and causing the thought which has been expressed that bedrock, being seen extending under the water, could not be more than a few feet below at the deepest place. But now this sloping rock can be seen to terminate abruptly, as though it were but a bench on the side wall of a deeper gorge. 30. But be the bedrock as it may, the site is well adapted to an overfall rock-fill dam of moderate height, which, owing to the high sheer bluff of sound rock, could be cheaply constructed; and considering the limited amount of water that would be impounded by it, whereby not much damage could result in the event of its release, such a dam would be permissible at this place, particularly if a dam shall first be built at the San Carlos site, which would intercept or moderate the floods. 31. Between the Needles Eye and the mouth of Hawk Canyon, some 2 miles above, is another promising dam site between walls of granite rock. Doubtless other sites exist below suitable for power development. It is to be remembered, however, that there is a limit to height and number of such dams, which should not be passed, for any great reduction in the average grade of the river would unsuit it for conveying silt when desilting operations shall be required. D. E. HUGHES. |